Semiconductor ignition



March 25, 1969 SCHNEIDER ET AL 3,434,462

SEMICONDUCTOR IGNITION Filed June 21, 1965 Sheet of 2 '8 FIG. I Is v SEMI CONDUCTOR i 6 IGNITION '4 o o oo 0 Q--- 32 I04 FIG.5 s I63 M/*Mino F|G.3

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? ALFRED SCHNEIDER BY WILLIAM F. SHUNN PAUL w. ROESKE ATTORNEYS March 25, 1969 $HNE|DE| ET AL 3,434,462

SEMICONDUCTOR IGNITION Filed June 21, 1965 Sheet 2 or 2 WWI, 9/

f ATTORNEYS nited States Patent 3,434,462 SEMICONDUCTOR IGNITION Alfred Schneider, Detroit, William F. Shunn, Fraser, and Paul W. Roeske, Grosse Pointe Farms, Mich., assignors to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed June 21, 1965, Ser. No. 465,606 Int. Cl. F02p 1/00; H05b 41/00 US. Cl. 123-148 Claims ABSTRACT OF THE DKSCLOSURE In the past semiconductor ignition systems, such as shown in commonly owned, herein incorporated, co-pending patent application Ser. No. 336,418, filed Jan. 3, 1964, now Patent No. 3,291,108, have provided protection for the switching semiconductor by means of a Zener diode connected across the emitter and collector of the switching semiconductor effective to limit the primary back voltage from the ignition coil to about one hundred volts. The Zener diode in the past has therefore limited the possible voltage of the spark whereby increased spark energy could only be obtained by higher current drain on the power supply which in the usual case is a limited storage battery. The expense and current drain inherent with Zener diode protection of the switching semiconductor has been considered necessary since without the Zener diode the switching semiconductor of past semiconductor ignition systems have failed apparently due to a high back voltage from the ignition coil produced by voltages in the ignition coil of sufficient magnitude to provide a spark having required energy at allowable current drain.

In experimental operation of semiconductor ignition systems without Zener diode protection for the switching semiconductor it was found that with the system disconnected from the spark plugs that the switching semiconductor could withstand considerably more back voltage than it was supposed to be able to and was able to with the spark plugs connected. Research into this phenomenon indicated that the lower break-down voltage of a switching semiconductor in an ignition circuit with the spark plugs connected is due to a very large radio frequency feed-back signal to the switching semiconductor from the ignition coil on firing of the ignition system. The radio-frequency feed-back signal may in practice reach one thousand volts and one hundred volts is typical.

It is therefore particularly desirable to provide radio frequency protection for the switching semiconductor. With such protection the relatively expensive Zener diode may be eliminated and voltage in the ignition coil increased to provide higher spark energy with less current drain and less heat which accompanied previously required high current drains.

Also, with pulse type semiconductor ignition systems as illustrated in the above referenced patent application, the circuit for generating a signal at a rate proportional to the speed of and synchronized with the operation of the engine has been found to be particularly sensitive to spurious signals, such as produced by cranking of the 3,434,462 Patented Mar. 25, 1969 engine starter, meshing of gears and even pounding on the engine during startup. The spurious signals are particularly detrimental to engine starting in that they produce firing of the ignition system with the pistons of an internal combustion engine, for example, in the wrong position, causing back-firing or bucking of the engine.

Further, in prior semiconductor ignition systems the initially produced pulse has sometimes been found to produce a train of pulses in the ignition circuit. This is particularly true in ignition systems wherein the synchronized initial pulse is differentiated for use in producing a switching signal for the switching semiconductor of the ignition system. Thus, a slow rising initial pulse synchronized with the engine operation may be differentiated three or four times before the pulse is dissipated. These multiple pulses are detrimental to operation of subsequent circuits in the ignition system or operating off of the ignition system on the basis of a sensed number of pulses such as some tachometers.

Also, in semiconductor ignition systems it is desirable to provide a tachometer to indicate engine speed. In the past such tachometers have been complicated and expensive to provide due to the poor regulation of power supplied to the ignition systems and the multiple pulses produced as indicated above. In addition the prior semiconductor ignition systems have been deficient in that the switching time of the switching semiconductor has been too long.

It is therefore one of the objects of the present invention to provide an improved semiconductor ignition system for internal combustion engines or the like.

Another object is to provide a pulsed semiconductor ignition system including a more economical circuit for providing more spark energy at less current drain than possible with prior similar semiconductor ignition systems.

Another object is to provide a semiconductor ignition system including improved switching semiconductor protection circuits.

Another object is to provide a semiconductor ignition system including a spurious signal suppression circuit.

Another object is to provide a semiconductor ignition system including a multiple signal suppression circuit.

Another object is to provide a semiconductor ignition system including an integral tachometer circuit.

Another object is to provide a semiconductor ignition system including an improved compensation circuit for fast switching of the switching semiconductor.

Another object is to provide a semiconductor ignition system including an improved power supply filter circuit.

Another object is to provide a protection circuit for a switching semiconductor.

Another object is to provide an improved compensating circuit for a switching semiconductor.

Another object is to provide an improved tachometer.

Another object is to provide a spurious signal suppression circuit.

Another object is to provide a multiple signal suppression circuit.

Another object is to provide a semiconductor ignition circuit which is simple in construction, economical to manufacture and efficient in use.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a partly block, partly schematic and partly diagrammatic diagram of an internal combustion engine and an ignition system including a semiconductor ignition circuit constructed in accordance with the invention in conjunction therewith.

FIGURE 2 is a schematic diagram of the semiconductor ignition circuit and a portion of the ignition system shown in FIGURE 1.

FIGURE 3 illustrates a modification of part of the portion of the ignition system illustrated in FIGURE 2.

FIGURE 4 illustrates another modification of part of the portion of the ignition system illustrated in FIG- URE 2.

FIGURE 5 illustrates still another modification of part of the portion of the ignition system illustrated in FIG- URE 2.

FIGURE 6 illustrates a modification of the spurious signal suppression part of the portion of the ignition system illustrated in FIGURE 2.

With particular reference to the figures of the drawings, one embodiment of the present invention will now be considered in detail.

The semiconductor ignition circuit 10 is illustrated in FIGURE 1 in a pulse type semiconductor ignition system 12, in conjunction with an internal combustion engine 14. The ignition system 12 besides the ignition circuit 10 includes a battery 16, ignition switch 18, distributor cam 20, an electric pulse producing device 22, ignition coil 24 and distributor 26. The ignition system 12 further includes the centrifugal distributor cam advance mechanism 28, engine vacuum advance apparatus and the spark plugs 32 connected between the engine 14 and distributor 26.

In operation of the ignition system 12, with the ignition switch 18 closed, the battery 16 provides electrical energy for the operation of the semiconductor ignition circuit 10. On rotation of the engine 14 and the distributor cam 20 mechanically connected thereto, the pulse producing device 22 provides a pulse of electric energy which is amplified and used to control the electric current flowing through the primary winding 34 of ignition coil 24. Cutting off of the current through the primary winding 34 of ignition coil 24 produces a pulse of electric energy in the secondary winding 36 of ignition coil 24 at distributor 26. Pulses of electric energy from the secondary winding 36 of ignition coil 24 are distributed by distributor 26 to the separate spark plugs 32 for firing fuel in the internal combustion engine 14 to produce rotation thereof.

Firing of the spark plugs 32 produces a considerable radio frequency signal which may be fed back through the ignition coil 24 to the semiconductor ignition circuit 10 to produce harmful effects on the components thereof. Therefore, in accordance with the invention a radio frequency filter circuit 38 is provided between the ignition coil 24 and the semiconductor ignition circuit 10 for isolating the semiconductor ignition circuit from the radio frequency signals produced on firing of the spark plugs 32.

The structure and operation of batteries 16, ignition switches 18, ignition coils 24, distributors 26, spark plugs 32 and centrifugal and vacuum operated spark advance mechanisms for distributor cams in conjunction with internal combustion engines are well known and will not be considered in further detail herein. The structure and operation of the pulse producing device 22 is set forth in detail in the above referenced copending patent application and the commonly owned patent applications referred to therein in a semiconductor ignition system similar to the present semiconductor ignition system. The particular pulse producing device 22 will not therefore be considered in detail herein. The particular semiconductor ignition circuit 10 is however shown in detail in FIGURE 2.

The semiconductor ignition circuit 10 includes the coil 40 of the pulse producing device 22 in which pulses of electric energy synchronized with engine rotation are produced on rotation of the distributor cam 20, a spurious signal suppression circuit 42 for suppressing high frequency extraneous electric signals that may be produced in the pulse producing device 22, and a pulse amplifier circuit 44 for amplifying the signals produced in the coil 40 and passed by the spurious pulse suppression circuit 42.

The semiconductor ignition circuit 10 further includes a differentiating circuit 46 for differentiating the amplfied pulses from the pulse amplifier circuit 44 to provide a trigger signal for the multivibrator circuit 48 and a multiple signal suppression circuit 50 between the differentiating circuit 46 and multivibrator 48 for suppressing multiple signals produced in the difierentiating circuit 46 corresponding to a single pulse of electric energy produced in the coil 40.

A tachometer circuit 52 is connected to the multivibrator circuit 48 to provide an indication of engine rotational speed.

The ignition circuit 10 further includes an emitter follower circuit 54 connected to receive the output signal from the multivibrator circuit 48 and to control a driver amplifier circuit 56 which in turn drives a switching circuit 58. The switching circuit 58 controls the current flow through the radio frequency filter circuit 38 and primary winding 34 of ignition coil 24.

A compensating circuit 60 for aiding rapid switching of the switching semiconductor 184 in the switching circuit 58 is provided in conjunction with the cathode follower circuit 54, driver amplifier circuit 56 and switching circuit 58. The power supply filter circuit 62 for filtering the electrical signal aipplied to the ignition circuit 10 from battery 16 on closing of the ignition switch 18 completes the ignition circuit 10.

More specifically a pulse of electric energy will be produced in the coil 40 each time a lobe or projection 64 on the distributor cam 20 passes the coil core member 66. Since the distributor cam 20 is driven at a speed directly proportional to the speed of the engine 14, the pulses produced in the coil 40 will be in timed relation to the speed of the engine 14 and provide a pulse of electric energy through the ignition circuit 10 at the distributor 26 to fire the spark plugs 30 in a predetermined sequence at desired times related to the rotational position of the engine 14.

The pulses produced in coil 40 and passed by the spurious signal suppression circuit 42 which will be considered later in detail are amplified through the pulse amplifier circuit 44 including the semiconductor 68 and load resistor 70. The emitter-collector circuit of the semiconductor 68 is connected in series with the load resistor 70 across the terminals of the battery 16 through the filter resistor 72 and diode 74 of the battery filter circuit 62. The base circuit of the semiconductor 68 is connected across the coil 40.

Thus, in operation, as a pulse is produced in the coil 40 and passed by the spurious signal suppression circuit 42, the produced pulse :biases the semiconductor 68 into operation to provide a relatively slow rising amplified pulse of electric energy across the load resistor 70.

The pulse of electric energy amplified in the pulse amplifying circuit 44 is differentiated through the differentiating circuit 46 which includes the resistor 76, capacitor 78 and diode 80. Thus, as the signal changes between the load resistor 70 and semiconductor 68 on conduction of the semiconductor 68, a charge is built up rapidly on capacitor 78 through the resistor 76 which has a relatively low value in comparison to the load resistor 70. The charging path for the capacitor 78 is through the base circuit of the semiconductor 82 forming the left half of the multivibrator circuit 48 in FIGURE 2 and through the thermistor S3 in parallel with the base circuit of the semiconductor 82 and through the series connected diode 50.

The differentiated signal on the capacitor 78 will trigger the monostable multivibrator 48 so that it will change operating state and the normally non-conducting semiconductor 82 will conduct for a predetermined time as set by the circuit constants of multivibrator 48. Conduction of the normally non-conducting semiconductor 82 will cause the normally conducting semiconductor 84 of the multivibrator circuit 48 to stop conducting. The

calpacitor 78 will then be discharged through the diode 80 to prepare the differentiating circuit 46 for subsequent differentiation of amplified pulses from coil 40 amplified through amplifier semiconductor 68.

The multivibrator circuit 48, as shown in FIGURE 2, includes the high gain normally non-conducting semiconductor 82 having an emitter-collector circuit in series across the battery 16 through the load resistor 86 and the normally conducting low gain semiconductor 84 having an emitter-collector circuit in series with the load resistor 88 across the battery 16. A feed-back capacitor 90 is provided between the collector of the semiconductor 84 and the base of the semiconductor 82, as shown in FIGURE 2, while a parallel combination capacitor 92 and resistor 94 are positioned between the collector of the semiconductor 82 and the base of the semiconductor 84.

In operation, on differentiating a pulse of electric energy in the differentiating circuit 46, bias will be applied to the semiconductor 82 of the multi-vibrator circuit 48 to produce an initial output from the semiconductor 82 at an exactly predetermined time with respect to the occurrence of an initial pulse in the coil 40. The duration of the conduction of the semiconductor 82 will depend on the time constant in the multivibrator feed-back circuit so that the output pulses provided by the multivibrator circuit 48 across the load resistor 86 will be exactly determined in width.

To stabilize this portion of the semiconductor ignition circuit 10, the electrical energy from the battery 16 is filtered through the filter circuit including capacitor 96 as well as the resistor 72 and diode 74 previously considered. The diode 74 is included in the power supply filter circuit to prevent discharge of filter capacitor 96 through battery 16.

Stabilization of the operation of the multivibrator circuit 48 at high temperature is further provided by the thermistor 83 positioned across the base circuit of the semiconductor 82, as shown in FIGURE 2. The thermistor 83 functions to lower the gain of the semiconductor 82 at high temperatures, thus preventing free running of the multivibrator circuit 48.

In operation of the pulse amplifier circuit 44, the differentiating circuit 46 and the multivibrator circuit 48 of the semiconductor ignition circuit it has been found that the capacitor 78 of the differentiating circuit 46 will discharge through the capacitor 90 on conduction of the semiconductor 82 without the multiple signal suppression circuit 50 between capacitors 78 and 90. This discharge of the capacitor 78 would then permit a second charging thereof due to the still present relatively slowly rising amplified pulse in the pulse amplifier circuit 44 to produce another trigger pulse for the multivibrator circuit 48 without another tpulse having been produced in the coil 40.

Due to the timing of the multivibrator and the time between the pulses produced in coil 40 synchronized with the rotation of the engine, it has therefore been possible in the past to provide an initial signal of exact predetermined width from multivibrator 48 corresponding to the desired rotational position of the engine. In addition to the desired signal, multiple signals from the multivibrator have therefore been produced of a number equal to the trigger pulses provided by the differentiating circuit. These multiple pulses are detrimental when subsequent circuit components function in accordance with the number of pulses received.

Thus, in accordance with the present invention, the multiple signal suppressing circuit 50 consisting of diode 51 positioned between the capacitor 78 and the capacitor 90 is provided in the semiconductor ignition circuit 10, as shown in FIGURE 2. Diode 51 permits bias current fiow through the semiconductor 82 of the multivibrator 48 but prevents reverse current flow through the diode 51 which would permit the capacitor 78 to discharge through the capacitor The emitter follower circuit 54 includes the semiconductor 98 in series with the load resistor 100" across the battery 16. In operation of the semiconductor ignition circuit 10, the semiconductor 98 is normally non-conducting. On conduction of the semiconductor 82 in the multivibrator circuit 48, the semiconductor 98, the base of which is connected between the semiconductor 82 and the load resistor 86 thereof, is caused to conduct. Conduction of the semiconductor 98 will cause the driver amplifier circuit 56 and therefore the switching semiconductor circuit 58 to stop conducting.

The driver amplifier circuit 56 includes the semiconductor 102 having the emitter-collector thereof connected between the base of the switching semiconductor 104 and one side of the battery 16 through load resistor 106. The base of semiconductor 102 is connected to the emitter follower circuit 54 between the semiconductor 98 and the load resistor 100 through resistor 108 in the compensating circuit 60. An emitter base, leak resistor 114 is also provided.

In operation the normally conducting driver amplifier semiconductor 102 carries the base current for the switching semiconductor 104 in its emitter-collector circuit. On conduction of the emitter follower semiconductor 98 due to a pulse applied thereto from the semiconductor 82 of the multivibrator circuit 48, the driver amplifier circuit semiconductor 102 is caused to stop conducting whereby the base current through switching semiconductor 104 is cut off and the switching semiconductor 10'4 switched to a nonconducting state.

The switching semiconductor circuit 58 includes the switching semiconductor 104 having the emitter-collector circuit in series across the battery 16 with the resistor of the radio frequency filter circuit 38 and the primary winding 34 of ignition coil 24. The base of the switching semiconductor 104 is connected in the emitter-collector circuit of the driver amplifier circuit semiconductor 102, as previously indicated, and is further connected to the compensating circuit 60, as shown in FIGURE 2. The usual emitter base leak resistor 116 is also provided.

In operation a relatively large quantity of current flows through the primary winding 34 of the ignition coil 24, resistor 110 and the emitter-collector circuit of switching semiconductor 104. When the switching semiconductor 104 is caused to cease conducting the current flowing in the primary winding 34 of ignition coil 24 is cut off sharply to induce an electrical signal in the secondary winding 36 of the ignition coil 24 which is distributed by the distributor 26 to spark plugs 30 to produce sparks in the cylinders of engine 14 and subsequent rotation of the engine 14.

The compensation circuit 60 is provided in conjunction with the cathode follower circuit 54, driver amplifier circuit 56 and switching circuit 58 to decrease the switching time of the switching semiconductor 104. The compensating circuit 60 includes the capacitor 120, diode 122 and resistor 118.

In operation, during conduction of the driver amplifier semiconductor 102 and the switching semiconductor 104, the capacitor 120 is charged in parallel with the resistor 108 in the base circuit of the semiconductor 102. The charge on the capacitor 120 at this time will be such as to tend to bias the conducting switching semiconductor 104 into a non-conducting condition. Thus, when the cathode follower circuit semiconductor 98 conducts to cause the driver amplifier and switching semiconductors 102 and 104 to stop conducting, the capacitor 120 will discharge through the diode 122, resistor 118 and the now conducting cathode follower semiconductor 98 to apply the charge thereon across the base circuit of the switching semiconductor 104 and tend to stop the conduction of the switching semiconductor 104 faster than it would otherwise be stopped to shorten the switching time of the semiconductor 104.

Prior compensating circuits wherein a capacitor has been provided across the resistor 114 as well as across the resistor 108 have been inefficient in that the capacitor placed across the resistance 114 tends to discharge into the capacitor 120 and retard the over-all compensation applied to the switching semiconductor 104. The positioning of a diode 122 and current limiting resistor118 across resistor 114 in place of the usual capacitor produces better compensation in that switching of the switching semiconductor 104 is accomplished quicker.

The tachometer circuit 52 includes resistor 124, rheostat 126, diodes 128 and 130, capacitor 132 and Zener diode 134 along with meter 136 connected as illustrated best in FIGURE 2. Resistor 124 is connected at the upper end thereof between the semi-conductor 82 of multivibrator 48 and the load resistor 86 therefor to receive a signal when the semiconductor 82 is conducting. Meter 136 provides integration of signals fed thereto due to the natural integrating action of the components thereof.

In operation, as previously indicated, pulses the number of which are directly proportional to the speed of engine 14 are provided in the coil 40 of pulse producing device 22 each of which cause conduction of multivibrator semiconductor 22 for a predetermined time. Spurious pulses are suppressed by the pulse suppression circuit 42 while multiple pulses are suppressed by the multiple pulse suppression circuit 50. Thus pulses of a predetermined width but of unknown amplitude are provided through resistor 124 in the tachometer circuit 52 at the ungrounded side of the Zener diode 134.

The Zener diode 134 performs a clipping function to provide a constant amplitude for each of the pulses received from the multivibrator circuit 48. The pulses passing the Zener diode 134 are then differentiated in the differentiating circuit including the capacitor 132 and diode 130 to produce positive and negative going impulses of predetermined size. The negative going pulses are then cut off by the diode 128 and the positive pulses of predetermined size are fed through the rheostat 126 to be integrated in the meter 136 where they provide an accurate indication of the speed of the engine 14.

The spurious signal suppression circuit 42 includes a capacitor 138 in series with the emitter-collector circuit of semiconductor 140 across the coil 40. The spurious signal suppression circuit 42 further includes the voltage divider resistors 142 and 144 positioned across the battery 16 and connected to the base of the semiconductor 140 to provide a predetermined initial bias on the semiconductor 140, an integrating circuit including the capacitor 146 and diode 148 and the coupling circuit including capacitor 150 and resistor 152 for coupling a predetermined signal from the driver amplifier circuit 56 to the spurious signal suppression circuit 42.

In operation, with the semiconductor 140 conducting, the pulses provided in the coil 40 due to rotation of the distributor cam which may be for example at a frequency or pulse repetition rate of between twenty and sixty cycles per second will be transferred to the pulse amplifier circuit 44 and will cause pulses from the multivibrator 48 to subsequently fire the spark plugs 30. However, spurious signals, such as caused by cranking of the engine 14, meshing of gears or even hammering on the motor 14 which have high frequency components that are picked up by the coil 40 are shunted through capacitor 138 and conducting semiconductor 1 40 to prevent the spurious signals from triggering the semiconductor ignition circuit 10.

At higher speed operation of the engine 14, such as rotation of the engine at one hundred revolutions per minute for example, the capacitor 138 tends to affect a retarding of the firing of the spark plugs with respect to the position of rotation of the distributor cam 20. This retarding of the spark produced by the ignition system 12 is undesirable.

- Therefore, the pulsed signal at the driver amplifier semiconductor 102 across resistor 106 is fed back through the coupling capacitor 150 and resistor 152 of the spurious signal suppression circuit 42 and across the integrating circuit comprising the diode 148 and capacitor 146 to produce a bias suflicient to cut off the semiconductor 140. The speed of rotation of the cam 20 at which the semiconductor is caused to cease conducting may be varied if desired by substituting a potentiometer for the resistor 106 and coupling the capacitor 150 to the wiper arm of the potentiometer as will be understood by those in the art.

Providing spurious signal suppression is required only during engine starting which is often the case, the same signal suppression function can be provided at greatly reduced cost, particularly in original equipment by use of the modified circuit shown in FIGURE 6. As illustrated in FIGURE 6, the transistor 140, capacitor 146,

iode 148 and resistors 144 and 152 are replaced by capacitor 139 in parallel with coil 40 with normally open relay contacts 141 closed. The relay contacts 141 are closed on energization of relay coil 143. Relay coil 143 is energized only when the usual engine starting circuit is energized to which it is connected by conductor 147. The coil 143 may be connected to the starter motor armature, the starter solenoid, the starter relay, or the starter switch in the usual engine starting circuit 145.

The semiconductor ignition system as thus far described in detail has usually included a Zener diode connected across the emitter-collector electrodes of the switching semiconductor 104. The Zener diode is relatively expensive. However, with the Zener diode, it has been considered in the past that the back voltage from the ignition coil 24 would be high enough to damage the semiconductor 104 when the voltage in the ignition coil 24 is sufficient to produce a spark of required energy at the spark plugs 32.

The Zener diodes normally limit the primary back voltage across the Zener diode to about one hundred volts. The energy in the spark at the spark plugs 32 can therefore only be increased by increasing the current through the semiconductor 104 which is detrimental in that the semiconductor 104 runs hotter and is therefore subject to early failure.

It is known that the usual switching semiconductors 104 can withstand voltages considerably higher than one hundred ten volts for short periods, such as is common in the occurrence of a back voltage from the ignition coil 24. At the higher voltages it has been observed that the semiconductors 104 failed at much lower voltages with the spark plugs of the ignition system 12 connected to the ignition coil 24 than with the spark plugs disconnected.

An investigation of this phenomenon has led to the discovery that besides the usual considered back voltage from the ignition coil 24, a radio frequency voltage of a magnitude which may even exceed the usual back voltage through the ignition coil 24 is fed from the spark plugs through the ignition coil to the switching semiconductor 104 to cause early failure of the switching semiconductor 104 without Zener diode protection thereacross. The radio frequency voltage presented at the switching semiconductor 104 on firing of spark plugs 32 may be as high as one thousand volts and is typically one hundred volts.

With the discovery of the high radio frequency voltage at the switching semiconductor 104 it is possible in accordance with the invention to delete the expensive Zener diode protection for the switching semiconductor 104 with the substitution of a radio frequency filter and protection circuit for the switching semiconductor 104. The radio frequency circuit will permit higher primary back voltages of for example three hundred volts across the switching semiconductor 104 to materially increase the energy in the spark at the spark plugs 32 with less current through the switching semiconductor 104 and therefore less heat produced and longer operating life of switching semiconductor 104. In addition, the radio frequency filter and protection circuits cost in the order of three to ten cents to provide as against a cost of about one dollar for the usual Zener diode for the switching semiconductor.

In other words, discovery of a previously unsuspected radio frequency voltage at the switching semiconductor 104 and the substitution of a relatively cheap radio frequency filter for the usual relatively expensive Zener diode protection across the switching semiconductor permitted by the discovery of the radio frequency voltage permits higher energy sparks at the spark plugs with less current drain from the battery 16 and cooler operation for the switching semiconductor 104 to prolong the life thereof.

The radio frequency filter circuit 38, best illustrated in FIGURE 2, includes the resistor 1.10 which provides ballast between the switching semiconductor 104 and the primary winding 34 of ignition coil 24, capacitor 152 positioned across the primary winding 34 of the ignition coil 24 to shunt radio frequencies fed back to coil 24 to ground, capacitor 154 which functions as a surge capacitor to limit the initial build-up of back voltage across semiconductor 104 and the radio frequency bypass capacitor 155 connected across the switching semiconductor 104, as shown in FIGURE 2.

Thus in operation of the radio frequency filter circuit 38, on switching off of the semiconductor 104 a back voltage from ignition coil 24, of for example three hundred volts, may be felt across the switching semiconductor 104 for a very short time which back voltage is lessened in rise time by the provision of the relatively large surge capacitor 154. Substantially simultaneously with the back voltage applied to the semiconductor 104 a radio frequency voltage will be fed back from the spark plugs 32 through the coil 24 and will be shunted to ground through the capacitor 152. Any part of the radio frequency signal which is not shunted to ground through the relatively small capacitor 152 will be bypassed around the switching semiconductor 104 by capacitor 155. Thus, with the radio frequency protection circuit 38 the switching semiconductor 104 is substantially unaffected by the radio frequency signal produced on firing of the spark plugs 32.

Other radio frequency filter circuits, such as illustrated in FIGURES 3, 4 and may be used in place of the filter circuit 38.

Thus, the filter circuit 156 illustrated in FIGURE 3 comprises the spark plates 158 placed across the emittercollector electrodes of the switching semiconductor 104 in the semiconductor ignition circuit, as shown in FIG- URE 3. The difficulty of connecting spark plates .158 makes their use less desirable than the filter circuit 38 illustrated in FIGURE 2. However, the radio frequency filtering efficiency of the spark plates 158 may be equal to that of the filter circuit 38.

The filter circuit 160 illustrated in FIGURE 4 includes a plurality of low capacity low dissipation factor capacitors 162 placed across the emitter-collector electrodes of the switching semiconductor 104. The efficiency of the filter circuit illustrated in FIGURE 4 may be equal to that of the filter circuit illustrated in FIGURE 2 with the cost slightly greater due to the number and type of condensers required and the number of connections therefor in the circuit 10.

The filter circuit 161, illustrated in FIGURE 5, includes 22 operably associated with the distributor cam 20 produces pulses at a rate proportional to the speed of the engine 14. Spurious pulses generated in the coil 40* of the pulse producing device 22 are suppressed by the spurious pulse suppression circuit 42 due to the relatively high frequency components thereof.

Pulses synchronized with the rotation of the engine 14 are amplified through the pulse amplifying circuit 44 and are differentiated in the differentiating circuit 46 to provide a trigger pulse for the multivibrator circuit 48. The multiple signal suppression circuit 50 prevents more than one trigger pulse for the multivibrator 48 due to one pulse amplified by the amplifier circuit 44. The monostable multivibrator circuit 48 then produces a pulse of predetermined width for each trigger pulse received thereby. The pulses from the multivibrator circuit 48 which are still synchronized with the engine are passed to the tachometer circuit 52 to provide an indication of the speed of the engine 14 and are simultaneously passed to the emitter follower circuit 54 to cause conduction of the emitter follower semiconductor 98. On conduction of semiconductor 98, the driver amplifier circuit 56 stops conducting to switch off the switching semiconductor circuit 58. The switching semiconductor 104 is caused to switch off rapidly by means of the compensating circuit 60 associated with the cathode follower circuit 54-, driver amplifier circuit 56 and switching semiconductor circuit 58.

Switching off of the normally conducting switching semiconductor 104 produces a pulse of electric energy through the primary winding 34 of ignition coil 24. A pulse of energy is thereby created in the secondary winding 112 of the ignition transformer 24 which is distributed by the distributor 26 to the spark plugs 30 for firing to produce sustained rotation of the engine 14 in the usual manner.

On firing of the spark plugs radio frequency energy is generated which is fed back through the ignition coil 24 to the switching semiconductor 104. The radio frequency signal is passed to ground and/or around the switching semiconductor 104 through the radio frequency filter 38 positioned between the ignition coil 24 and switching semiconductor 104 and across the switching semiconductor 104.

When the pulse repetition rate through the semiconductor ignition circuit 10 exceeds a predetermined value, the transient signal suppression circuit 42 which is not as desirable at high engine speeds is deenergized to prevent spark retardation by the circuit 42 which would otherwise occur at high speeds.

While one embodiment of the present invention and modifications thereof have been considered in detail, it will be understood that other embodiments and modifications are contemplated. It is the intention to include all embodiments and modifications as are defined by the appended claims within the scope of the invention.

What we claim as our invention is:

1. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed including a member rotatable at engine speed, a cam secu ed to said member for rotation therewith having a plurality of lobes thereon, a coil positioned adjacent the cam for developing electric pulses in accordance with the passing of the lobes by the coil, a pulse amplifying circuit connected to the pulse producing mean for amplifying the developed pulses including an amplifying semiconductor having emitter, base and collector electrodes, said pickup coil being connected between the base and emitter electrodes, said collector electrode being connected to one side of the battery through an amplifier resistor, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, comprising a resistor, capacitor and diode connected in series between the collector electrode of the amplifying semiconductor and the one side of the battery, a multivibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, including a pair of semiconductors having emitter, base and collector electrodes, the emitter electrodes of which are connected to the one side of the battery, the collector electrodes of which are connected through multivibrator resistors to the other side of the battery, the base electrode of the first of said multivibrator semiconductors being connected to the differentiating circuit between the capacitor and diode thereof, the base electrode of the other of the multivibrator semiconductors being connected to the collector electrode of the one multivibrator semiconductor through a resistor and capacitor in parallel, a thermistor connected between the emitter and base electrodes of the one multivibrator semiconductor, a capacitor being connected between the base electrode of the one multivibrator semiconductor and the collector electrode of the other multivibrator semiconductor, an emitter follower circuit connected to the multivibrator circuit operable to conduct only on reception of a pulse from the multivibrator circuit, including an emitter follower semiconductor having emitter, collector and base electrodes, the emitter electrode being connected through an emitter follower resistor to the other side of the battery, the collector electrode being connected to the one side of the battery and the base electrode being connected to the collector electrode of the one multivibrator semiconductor, a normally conducting driver amplifier circuit connected to the emitter follower for cut-off on conduction of the emitter follower circuit, including a driver amplifier semiconductor having emitter, collector and base electrodes, the emitter electrode of which is connected to the one side of the battery through a first driver resistor, the collector electrode of which is connected to the other side of the battery through a second driver resistor, and the base electrode of which is connected to the emitter electrode of the emitter follower semiconductor through a third driver resistor and a fourth driver resistor connected between the emitter and base of the driver semiconductor, a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition coil on and off connected to the driver amplifier circuit for switching on and off in accordance with the state of conduction of the driver amplifier circuit, including a switching semiconductor having emitter, collector and base electrodes, the emitter electrode being connected to the one side of the battery, the collector electrode of the switching semiconductor being connected through the primary winding of the ignition coil to the other side of the battery, and the base electrode of the switching semiconductor being connected to the emitter electrode of the driver amplifier, and a radio frequency protection circuit operably associated with the switching semiconductor for preventing break-down of the switching semiconductor due to a radio frequency feed-back from the ignition system, including a radio frequency bypass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency bypass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

2. Structure as set forth in claim 1 and further including a spurious signal suppression circuit connected between the pulse producing means and the pulse amplifying circuit for suppressing signals having high frequency components and means for suppressing the spurious signal suppression circuit at high engine speeds, comprising a spurious signal suppression semiconductor having emitter, collector and base electrodes, a capacitor connected between the base of the amplifier semiconductor and the emitter electrode of the spurious signal suppression semiconductor, the collector of the spurious signal suppression semiconductor being connected directly to the other side of the battery, a pair of spurious signal suppression resistors connected between the opposite sides of the battery, the base electrode of the spurious signal semiconductor being connected to the junction between the two spurious signal suppression resistors, a diode and capacitor connected in series between the base electrode of the spurious signal suppression semiconductor and the collector electrode of the driver amplifier, a third spurious signal suppression resistor connected between the diode and capacitor in series at one end and the other side of the battery at the other end, and a capacitor connected between the base electrode of the spurious signal suppression semiconductor and the other side of the battery.

3. Structure as set forth in claim 1 and further including a multiple signal suppression circuit comprising a diode connected between the junction of the capacitor and diode in the differentiating circuit and the base electrode of the one multivibrator semiconductor for limiting the output of the differentiating circuit to a single trigger pulse for the multivibrator for each pulse received by the differentiating circuit from the pulse amplifying circuit.

4. Structure as set forth in claim 1 and further including a compensating circuit connected to the emitter follower circuit, driver amplifier circuit and switching circuit for providing a voltage tending to cut off the switching semiconductor during switching of the switching semiconductor to decrease the switching time thereof, comprising a resistor and diode in series with each other and connected between the emitter and base electrodes of the driver amplifier, and a capacitor connected between the emitter electrode of the emitter follower semiconductor and the base electrode of the driver amplifier semicondoctor.

5. Structure as set forth in claim 1 and further including a filter circuit for filtering electric energy applied to the ignition circuit integral with the ignition circuit, including a diode, resistor and capacitor connected in series across the battery.

6. Structure as set forth in claim 1 and further including a tachometer circuit connected to the multivibrator for providing an indication of the speed of the engine associated with the ignition circuit, comprising a tachometer, resistor and Zener diode connected in series between the collector of the one multivibrator semiconductor and the other side of the battery, a capacitor, diode, variable resistance and indicating meter connected in series across the Zener diode and a diode connected between the capacitor and diode in series on one side and the other side of the battery on the other side.

7. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multi-vibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined Width each time a trigger pulse is received thereby, an emitter follower circuit connected to the multi-vibrator circuit operable to conduct only on reception of a pulse from the multivibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-off on conduction of the emitter follower circuit, a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition coil on and oil? connected to the driver amplifier circuit for switching on and otf in accordance with the state of conduction of the driver amplifier circuit and a radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system, including a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter re sistor and the other side of the battery.

8. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed including a member rotatable at engine speed, a cam secured to said member for rotation therewith having a plurality of lobes thereon, a coil which is adjacent the cam for developing electric pulses in accordance with the passing of the lobes by the coil, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses including an amplifying semiconductor having emitter, base and collector electrodes, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multi-vibrator circuit connected to the dilferentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, an emitter follower circuit connected to the multi-vibrator circuit operable to conduct only on reception of a pulse from the multivibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-off on conduction of the emitter follower circuit, a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition coil on and off connected to the driver amplifier circuit for switching on and off in accordance with the state of conduction of the driver amplifier circuit and radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system, including a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected-t the opposite ends of the filter resistor and the other side of the battery.

9. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses including an amplifying semiconductor having emitter, base and collector electrode, a differentiating circuit connected to the pulse amplifying circuit for dilferentiating the amplified pulses to provide trigger pulses therefrom, comprising a resistor, capacitor and diode connected in series between the collector electrode of the amplifying semiconductor and the one side of the battery, a multi-vibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, an emitter follower circuit connected to the multi-vibrator circuit operable to conduct only on reception of a pulse from the multi-vibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-olf on conduction of the emitter follower circuit,

a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition coil on and otf connected to the driver amplifier circuit for switching on and olf in accordance with the state of conduction of the driver amplifier circuit, and a radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system, including a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

10. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multi vibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, including a pair of semiconductors having emitter base and collector electrode, the emitter electrodes of which are connected to one side of the battery, the collector electrodes of which are connected through multi vibrator resistors to the other Side of the battery, the base electrode of the first of said multi-vibrator semiconductor being connected to the differentiating circuit, the base electrode of the other of the multi-vibrator semiconductors being connected to the collector electrode of the one multi-vibrator semiconductor through a resistor and capacitor in parallel, a thermistor connected between the emitter and base electrodes of the one multi-vibrator semiconductor, a capacitor being connected bet-ween the base electrode of the one multi vibrator semiconductor and the collector electrode of the other multi-vibrator semiconductor, an emitter follower circuit connected to the multi-vibrator circuit operable to conduct only on reception of a pulse from the multi-vibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-01f on conduction of the emitter follower circuit, a switching circuit connected between the battery and igni tion coil for switching current between the battery and ignition on and off connected to the driver amplifier circuit for switching on and oif in accordance with the state of conduction of the driver amplifier circuit and a radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system, including a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

11. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multi-vibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, an emitter follower circuit connected to the mnlti-vibrator circuit operable to conduct only on reception of a pulse from the multi-vibrator circuit, including an emitter follower semiconductor having emitter, collector and base electrodes, the emitter electrode being connected through an emitter follower resistor to the other side of the battery, the collector electrode being connected to the one side of the battery and the base electrode being connected to the multi-vibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-off on conduction of the emitter follower circuit, including a driver amplifier semiconductor having emitter, collector and base electrodes, the emitter electrode of which is connected to the one side of the battery through a first driver resistor, the collector electrode of which is connected to the other side of the battery through a second driver resistor, and the base electrode of which is connected to the emitter electrode of the emitter follower semiconductor through a third driver resistor and a fourth driver resistor connected between the emitter and base of the driver semiconductor, a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition coil on and off connected to the driver amplifier circuit for switching on and off in accordance with the state of conduction of the driver amplifier circuit, and a radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system including a radio frequency by-pass capacitor connected between the emitter and base electrode of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

12. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multivibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, an emitter follower circuit connected to the multivibrator circuit operable to conduct only on reception of a pulse from the multivibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for out-off on conduction of the emitter follower circuit, a switching circuit connected between the battery and ignition coil for switching current between the battery and ignition on and off connected to the driver amplifier circuit for switching on and off in accordance with the state of conduction of the driver amplifier circuit, including a switching semiconductor having emitter, collector and base electrodes, .the emitter electrode being connected to the one side of the battery, the collector electrode of the switching semiconductor being connected through the primary winding of the ignition coil to the other side of the battery, and the base electrode of the switching semiconductor being connected to the driver amplifier circuit, and a radio frequency protection circuit operably associated with the switching semiconductor for preventing breakdown of the switching semiconductor due to a radio frequency feedback from the ignition system, including a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor, a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

13. A semiconductor ignition circuit for use in an ignition system including a battery and an ignition coil having a primary winding in conjunction with an internal combustion engine or the like, comprising means for producing pulses at a rate proportional to engine speed, a pulse amplifying circuit connected to the pulse producing means for amplifying the developed pulses, a differentiating circuit connected to the pulse amplifying circuit for differentiating the amplified pulses to provide trigger pulses therefrom, a multi-vibrator circuit connected to the differentiating circuit for receiving the trigger pulses and producing a pulse of predetermined width each time a trigger pulse is received thereby, an emitter follower circuit connected to the multi-vibrator circuit operable to conduct only on reception of a pulse from the multivibrator circuit, a normally conducting driver amplifier circuit connected to the emitter follower for cut-off on conduction of the emitter follower circuit, a switching circuit connected between the battery and ignition coil including a switching semiconductor for switching current between the battery and ignition coil on and off connected to the driver amplifier circuit for switching on and off in accordance with the state of conduction of the driver amplifier circuit and a radio frequency protection circuit operably associated with the switching circuit for preventing break-down of the switching semiconductor due to a radio frequency feedback from the coil of the ignition system.

14. Structure as set forth in claim 13 wherein the radio frequency protection circuit includes a radio frequency by-pass capacitor connected between the emitter and base electrodes of the switching semiconductor.

15. Structure as set forth in claim 13 wherein the radio frequency protection circuit includes a filter resistor connected between the collector electrode of the switching semiconductor and the primary winding of the ignition coil and a pair of parallel radio frequency by-pass capacitors connected between the opposite ends of the filter resistor and the other side of the battery.

References Cited UNITED STATES PATENTS 2,852,589 9/1958 Johnson 3l5209 2,955,248 10/1960 Short 3 15-409 3,178,608 4/1965 McKendry 123148 3,214,636 10/1-965 Dilger 315209 3,262,438 7/ 1966 Holford l23148 3,264,521 8/1966 Huntzinger 123-148 2,238,915 4/ 194-1 Peters 123-448 X 2,968,296 1/1961 Kaehni 315--209 X 3,202,146 8/1965 Short et al. 123-148 3,217,216 11/1965 Dotto 123-148 3,220,396 11/1965 Heidner et al. 123148 3,280,810 10/1966 Worrell et a1 123l48 3,291,108 112/1966 Schneidner et al 123-148 3,297,009 1/1967 Sasaki et al 123-148 3,299,876 1/ 1967 Mieras l23148 LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 315-209 

